How to distinguish between surgical and non-surgical pneumoperitoneum?

Not all cases of pneumoperitoneum found on abdominal X-ray or computed tomography (CT) scan are caused by hollow viscus perforation. Non-surgical or spontaneous pneumoperitoneum is a repeatedly described entity. However, not all physicians in emergency departments are aware of it, and in such cases unnecessary laparotomy is often performed which reveals no intra-abdominal pathology. Non-surgical pneumoperitoneum can have thoracic, abdominal, gynecological, or other causes. When we acknowledge the possibility of non-surgical pneumoperitoneum, the primary goal is to discern surgical from non-surgical pneumoperitoneum. Identifying cases in which laparotomy can be avoided is important to prevent unnecessary surgery and its associated morbidity and financial costs. In this paper we propose a practical algorithm which may help the attending physicians to distinguish between surgical and non-surgical pneumoperitoneum.